Combined manual and automatic route control system for railroads



Dec. 25, 1956 F. T. PASCOE 2,775,689

COMBINED MANUAL AND AUTOMATIC ROUTE CONTROL SYSTEM FOR RAILROADS Filed July 27, 1951 5 Sheets-Sheet l INVENTOR. Frank T Pascoe BY 71 2?/ M HIS ATTOIZJVE F. `T. PAscoE 2,775,689 COMBINED MANUArJ AND AUTOMATIC ROUTE CONTROL SYSTEM FOR RAILROADS Dec. 25,y 1956 Filed July 27 1951 5 Sheets-Sheet 2 RIW AzyW :fr Nm@ m @I AA INVENTOR. mmm Bl? Frank ZPascoe m y. )5, ZbW/1W, @il 11 HIS ATTUHVEY Dec 25, 1956 F. T. PAscoE 2,775,689

COMBINED MANUAL. `AND AUTOMATIC ROUTE CONTROL SYSTEM FOR RAILROADS Filed July 27, 1951 5 Sheets-Sheet 3 IN V EN TOR.

Frank 7? Pascoe Hfs A TToHNl/J'Y' Dec. 25, 1956 F. T. PAscoE COMBINED MANUAL ANO AUTOMATIC ROUTE CONTROL SYSTEM FOR RATLROADS 5 Sheets-Sheet 4 m w wrm www D Sak m u m w m www www @Se @E S .2% www w Hm Tmlmn SN NN V1-5. NN mm Z :NNE n Filed July 27, 1951 JNVENTOR. Frank 7? Pascoe HIS ATTORNEY 5 Sheets-Sheet 5 F. T. PASCOE CONTROL SYSTEM FOR RAILROADS COMBINED MANUAL AND AUTOMATIC ROUTE Dec. 25, 1956 Filed July 27, 1951 miammi guai mi; illu-ll INVENTOR. Frank 7? Pascoe 2a. z. M

HIS ATTRNEY' 55.@ IPIIIIIL .m w .w A z w .Q .v .IV n

M 1w f E E w v 11V nu. Q m R m E United States Patent O COMBINED MANUAL AND AUTOMATIC ROUTE CONTROL SYSTEM FOR RAILROADS Frank T. Pascoe, Scott Township, Allegheny County, Pa., assgnor to Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Application July 27, 1951, Serial No. 238,799 15 claims. (Cl. 246-2) My invention relates to a combined manual and automatic route control system for railroads by means of which, -at the will of ,an operator, certain trafc rou-tes over the track switches of a manually controllable interlocking plant may beset up and the corresponding entering signals cleared automatically in accordance with the destinations of approaching trains.

More particularly, my invention relates to the automatic control of the switches and signals of an interlocking plant by a train describer system of the type :adapted to automatically and successively -display at .a wayside `station indications of the route, class or destination of each of a series of trains which lapproach the station over the same stretch of railway track, |and. in which the indication of each train is cancelled upon its arrival at the station land then superseded by the indio tion for the next following train.

My invention is particularly adapted for use in connection with a train describer system of the type in which the route indications are both supplied and cancelled automatically by the action of route identifying marker devices on the approaching trains without dependence upon track circuits for indicating the arrival or departure of such trains. p

The primary object of my invention is to provide the maximum protection .against improper operation of the track switches 'and signals under conditions ,involving their automatic operation as `the result of train movements.

A specilic object of my invention is to Provide improved manual change-over or transfer means for placing the switches and signals alternatively under manual control, or under automatic control by a train describer system. This change-over means functions in `such a manner as to insure that ia shift to automatic control will be made only when no vtrain is |approaching within a predetermined distance of the automatically controllable routes Ior is occupying one of lthese routes -or a conieting route.

A feature of my invention resides in the control of this change-over means so `that the system automatically terminates the automatic control upon the approach of la train which is not identiie-d by 'the train describe-r system, with the object of insuring Ithat a route will not be set up for an unidentified train as the result, for example, of the storage in the train describer system of a route indication fora following trai-n.

A Vfurther object of my invention is the provision of additional protection under automatic operation against the release of the usual switch locking during the passage of a train over :a route due to poor shunting of a track relay or the like. Conventionally, under manual operation, la circuit for rendering the switch locking ineffective is prepared by energizing Aan approach locking stick relay by the release of a track relay when a train enters a route and the circuit is completed by the energization of the same or of another track relay when the route is vacated. In accordance with a feature of y 2,775,689 Patented Dec. 25, 1956 "ice y my invention the approach locking relay does not become energized when a train enters the route but remains released to maintain the switch locking effective until the end of a predetermined time interval which does not begin until the train has vacated the route.

This feature of my invention is .applied to Ithe locking for each route which conflicts with an automatically controllable n route. i f

In the following one ,form of apparatus embodying my invention will be described and the novel features thereof will -then be pointed 'out in claims.

In the accompanying drawings, Fig. 1A shows ya diagram of a stretchof railway track equipped Iwith an interlocking control system Iarranged for automatic con` trol by a train describer system, in accordance with my invention, together with the circuits and apparatus of the train describer system by means of which approaching trains automatically indicate their route, class or destination by the selective lighting of one of the lamps in fa display indicator shown at the lower right in this view. Fig. 11BV -shows circuits tor the route selecting relays of an interlocking con-trol system of the route type controllable by push buttons which designate the opposite ends of the different routes, with the circuits modified to include the change-over means of my invention together with relays governed thereby which enable the train desc-riber system `to :automatically operate the selecting relays for certain routes. Fig. 1C shows a diagram of that portion 'of the track plan of Fig. 1A which includes the interlockedtratiic routes, together with circuits `and apparatus governed by the route selecting relays and by locking relays in accordance with signal and Itrack conditions, for .operating the interlockedv track switches and for indicating their position. Fig. 1D shows circuits for route relays controlled by the route select-ing and switch indication lrelays for governing the clearing of 'the signals. lFig. 1E shows circuits for :the mechanisms for Ithe entering signals for the i-nterlocked trahie routes, together with a diagram `of the -same portion of ythe track plan as is shown in Fig. 1C. Finally, Fig. lIF shows circuits for approach and time locking relays controlled by the route relays and by the signals, by means of which lthe track switches :and opposing 4signals are electrically interlocked.

Similar reference characters refer to similar parts in each of the several views, and Ito simplify the circuit diagrams, only the terminals of the local sources of current for energizing lthe various relays are shown, these being identiiied by the reference characters B |and N, respectively.

Referring to Fig. 1A, it is to be understood that the track 4plan lshown .is a portion 'of :a railroad employing electric traction. In the plan, the rails are represented diagrammatically by a single line, and it is to be understood that the rail-s are divided by insulated joints to form the series of |track `'sections 1T, 2T, 10T, 12T, 14T and 16T, each of which is equipped with a normally closed alternating -current track circuit having a Icorrespondingly numbered track relay TR supplied with energy over the rails of its section from a suitable source of alternating current designated-BX.

To simplify the drawings, only the minimum amount of appara-tus deemed necessary to illustrate the principles of my .invention is shown, .and accordingly, the interlocking plant shown is one having only a single pair of power operated trackswitches 1A and 1B, and the train describer system is arranged to provide only two route indications. The various routes through the plant will be designated `by the numbers which identify the Isignals at their opposite ends, as in Fig. 1\C, and they include the routes 2-6,2-'8 .and 4-8 having the entering signals 2A, 2B and 4, respectively, andthe opposing routes 454-2,

8-2 and '8-4 for which theentering signals `are 6, 8B and 8A, respectively. Of these, only the routes 2 6 and '2-8 are controllable automatically.

The-approach zone tor signals 2A `and 2B comprises the track sections 10T, i12/T and f14T, and its occupancy by a train is indicated in the conventional manner by the release of an approach relay |`ZAR controlled over front contacts a of the track relays lIOTR, 12TR and 14TR for these sections. v

Relay ZAR yand the track relays lTR and ZTR control indication lamps on an illuminated track diagram, not shown herein, by means of which the positions and movements 1of trains .are indicated in a control tower in ac- .v

cordance with the usual practice.

Briey described, the apparatus of my invention includes a manual change-over switch operable between two positions for designating manual and automatic control, respectively, which is incorporated in the route selecting push button ZPB, Fig. 1B, of the interlocking control system, together with a change-over stick relay APBS which may be picked up to transfer the system from manual to automatic control by Vpressing the button ZPB when` the change-over `switch is in its automatic position, but only if `the automatically controllable routes are unoccupied and the approach zone therefor is also unoccupied. The circuits incorporate the non-storage principle to insure that the transfer to automatic control will be made only under manual supervision and ywill not be made runder my unsafe traic conditions relative to the switch lo cking.

When relay APBS is energized, the route selecting relays of Fig. 1B by which routes 2 6 and 2-8 are established are controllable automatically by the repeating relays All and BP, respectively, governed by the train described :system in accordance with the indicated route .for the approaching train. When the automatic control is in elect, the manual control of non-conficting routes is not interfered with, for example, route 4-'8 or 8-J4 may be set up manually, except `when route 2-8 is set up.

In accordance with a feature of my invention, the change-over relay APBS is maintained energized either 'by the track relay 14T-R for the entering section 14T` of the approach zone, or by a directional stick relay 1-4SR controlled by relay 14TR and by the train describer system, in such a manner that relay xAPBS releases to disable the automatic control on the approach of any train which fails to actuate the train describer system to register an indication of its route.

This is desirable for the reason that the route for any train which does not actuate the train describer system should be set up by rnanual control. If this is -noft done, the Iautomatic control system would be in condition to be actuated by a following train upon entering the' occupied approach zone to set up a route which although established by the second train could be accepted by the tirst train regardless of the wishes of the operator, with the result that he would lose control of Ithat train. It will be clear that this difficulty is avoided by the automatic release of the change-over relay APBS in the event that a transfer from automatic to manual control, under the conditions described, has not already been made manually.

In addition, relay APBS when energized opens the circuits in IFig. lIF by which otherwise an approach locking relay AS controlled by the entering signal would be re-energized automatically when a train enters an established ro-ute.

Under manual operation, although the release of the track relays for the switch `sections is dependedupon primarily to insure that the switches will remain locked until the route is vacated, additional protection is provided by incorportating the non-storage principle in the switch control circuits. In accordance with this principle, if the control means is operated when the switches are locked, the result is merely to hold them locked, and the control means must be restored to its original condition and reoperated at a time when the switches of the route are not locked, in order to effect their operation. yIn order to provide a corresponding measure of additional protection under automatic operation, the circuits of my invention are arranged to maintain the switch locking effective after a route has been occupied, until it is cer- -tain -that it has been vacated as manifested 'by the fact that `the track relay has remained steadily energized for a predetermined time locking period during which the track relay for each section of Ithe route is steadily energized.

Before describing the operation of the apparatus of my invention in detail, the block signaling system, the train describer system and the interlocking control ysystem will each be briefly described, for the reason that knowledge of the general mode of operation of these systems is deemed necessary vfor an understanding 4of my invention.

Considering rst, the signaling system, it is to be y'undcrstood that the trains which traverse the stretch of track shown are equipped with `'automatic speed control and cab signaling apparatus of the well-known continuous inductive type, such as is illustrated Itypically in Letters Patent of the United States No. 2,235,037, granted March 18, 1941, to F. H. Nicholson et al. lThis' apparatus is controlled by periodically interrupting or coding the .alternating track circuit current supplied to the rails, at different rates, and in such a manner as to provide an overlap block system of control so that, `for example, when signals `ZA and 2B indicate stop, as shown, the aspects of the cab signals on an approaching train correspond -to those indicated by the wayside signal symbols 10, 12, 14 Iand 16. That is to say, an approaching train will 4be governed by a green proceed signal in section 16T, by a yellow 4over green approach medium signal in Section 14T and by a yellow approach signal in section `12T, due to the fact that the alternating current supplied to the rails of these sections is coded, by means not shown, 'at the respective rates of 180, 120 and 75 interruptions per minut-e, as indicated by the numbers directly below the corresponding sections on the track diagram. Steady alternating current is supplied to the rails of section 10T,

that is, this current is not coded and consequently the cab signaling equipment is nonresponsive thereto, so that a red stop signal is received and in addition an automatic brake application is incurred, if t-he train enters section 10T, in order to insure against overrunning signal 2A when section 1T is occupied or switch 1A is being operated. Corresponding protection is provided `for a train in -any of the sections; thus when a train stands in section 14T, steady or noncoded current is supplied to the rails of section 16T so that a following train on entering that section receives a red signal and is stopped before it reaches section 14T. Further consideration of the coded track circuits is not needed for an understanding of my invention, and accordingly these are represented as ordinary track circuits. It is to be understood that each track relay TR as shown is normally energized and that it releases when the rails of its section are shunted by a train .and also in the event of Ia failure of the track circuit supply.

The train describing system employed in connection with rny invention as shown in Fig. 11A includes two similar train reporting devices TDll and TD2 controllable by train carried marker coils and located respectively at the entrance to the approach zone and at the entrance to thevinterlocking plant, in the rear of signal ZA,l together with a storage indicator of the multiple unitA typeconytrolled thereby, which comprises a pluralit'yo'f cascade connected units adapted to .store indications'of the route, class or destination of the trains for display in the order of their passage through the approach zone.

This train describer system is of the type disclosed and claimed in 1a copending application for Letters Patent of the United States, Serial No. 238,616, `filed on June 26,

1951, by Henry J. Groenendale, nowUnited States P-atent Number 2,670,434 granted February 23, 1954.

In addition to its 1use for automatic route control purposes, an important function ofthe train descrilber system is to selectively light one of a plurality of lamps AE, BE, etc., to visua-lly indicate the route, cl-ass or destination of an approaching train or the approach .of an unclassified train. These indications may be displayed in a control tower for the guidance of an operator in setting up routes manually and also on a passenger station platform for the information of 4the public. The lighting of lamp AE indicates that the approaching train is to take route F6; the lighting of lamp BE indicates itis for route 28; while the lighting of lamp NE indicates `the approach of an unclassiiied train, that is to say, one lfor which the route is not specified and for which a route must be set up by manual control. ln addition, the `train describer system permits work trains or the like which are not equipped with marker coils to move into or tout of the approach zone lwithout interference with the displayed indication.

The relative length -of the approach zone with reference to the length and spacing of trains is assumed to be such that there is room for only two trains in the approach zone at the same time, and accordingly the storage indicator as shown compri-ses only two storage units. The 'first of these governs the display of indications by the lamps AE, BE and NE and comprises a lockout relay L1 land a plurality of indication storage relays A11, Bil and N1 of which one is provided for each indication to be displayed.

The second storage unit comprises the similar relays L2, A2, B2 and N2, and provides means tfor temporarily .storing .the indication for a second train` which enters the .approach Zone at a time when the tirst unit is displaying the indication for a preceding train.

Any suitable arrangement of storage relays may lbe used, but the storage indicator shown herein is of the type disclosed and claimed in Letters Patent of the United States No. 2,171,756, granted September 5, I1939, to Lloyd V. Lewis. p

The train reporting devices TD1 and TD2 may be of any suitable type, .but as shown herein these correspond, in principle, to what is'disclosed and claimed in a lcoipending application for 'Letters Patent of the United States, Serial No. 213,776, iiled March 3, 1-95ll, lby Richard Treharne, which has iss-ucd as Patent Number 2,753,550, dated July 3, 1956.y

@Each tra-in reporting device includes a plurality of primary windings continuously supplied with alternating current of a distinctive frequency f1, f2 or f3, which identifies the indication to be displayed by the :corresponding one of the lamps AE, BE and NE. Each primary Winding has an associated secondary winding to which it is effectively couple-d only when a train carried coil tuned to resonance at the corresponding frequency is interposed, or at least is brought into Iproximity with the correspond ing pair .of windings. Under this condition a detector relay \AD, BD or ND is operated by energy supplied by the corresponding secondary winding.

:llt will 'be evident therefore that when a train or vehicle V which is equipped with a coil tuned Vto resonance 'at any one of .the frequencies f1, f2 or f3 passes the reporting device TD1, 'the corresponding detector Irelay AID, BD or ND will be momentarily and selectively energized.

The train reporting device TD2 is :similar to TD1 but has all of its secondary windings connected to the same detector relay CN, and this relay is operated nonselectively when a vehicle V which operated relay AD, BD or ND on passing dev-ice TD1 passes the second reporting device TD2,

When a 'Vehicle V equipped with a marker coil passes the reporting device TD1, a distinctive indication'is registered by relay AD, BD or ND and is stored by energizing the corresponding relay of the second unit until the first unit is available, and is then transferred to the cor- 6 responding' relay of the first unit, which stores the indication until the'train passes the second reporting device TD2, and the indication is then cancelled by the operation of detector relay CN.

The indication may also be cancelled lby the operation of an emergency key ONB.

The train identification received by the train reporting device 'IlDl is stored in the following manner, provided the second storage unit is available with relays A2, B2 and N2 released, and rel-ay L2 energized as shown.

The operated detector relay AD, BD or ND energizes, over contact b of relay L2, the corresponding one of the storage relays A2, B2 or N2 which relay is held energized over a stick circuit and its contact d assumes its upper position, releasing relay L2, and if relays A1, B1 and N1 of the first unit are released, energizing relay L1. The energized relay A2, B2 or N2 then energizes, over contact b of relay L1, the corresponding storage relay A1, B1 or N1 of the first unit which by closing its contact e lights the corresponding lamp AE, BE or NE, and completes a stick circuit which holds the relay energized until relay CN is operated by the corresponding train on passing device TD2 to cancel its indication.

The stick :circuits for the storage relays A2, B2 and N2 of the second storage unit have two connections to terminal B of the local source of energy, one of which includes back contact d of relay L1, which is now open, and the other of which includes back contacts d of relays A1, B1 and N1. The latter connection is opened when one of these relays picks up to release the energized storage relay A2, B2 or N2, which in turn releases relay L1 and reenergizes relay L2. This renders the second unit available for the reception of an indication of a second train from the reporting device TD1 where it will be stored until the first storage unit is again rendered available.

Heretofore train describer systems as used commercially have been arranged to count train movements by the occupancy of certain track circuits to insure that at least one and only one indication will be stored or cancelled for eachtrain passage. This arrangement presents the practical difficulty that close manual supervision is required to properly corelate the stored indications with the corresponding trains due to the occasional occupancy of the controlling track sections by unidentified or unclassified trains or when switching movements have to be provided for involving the repeated occupancy of the track section at one end only of the controlled territory,

or in the event a second train enters a controlling track l section before it is vacated by a first train. A further diliiculty is presented where alternating current track circuits are used, as in the system herein disclosed, due to the possibility of the temporary release of a track relay used to count train movements, as the result of a fault or switching in the alternating current power network from which the track circuit derives its energization.

These difliculties are avoided in the train describer system shown because its operation is wholly independent of track circuit conditions. In consequence, the system is nonresponsive to irregular train movements or to the passage of eXtra trains unless this is desired, in which case the system is readily made responsive by the provision of suitably tuned coils on such trains, and the system is particularly well adapted to automatic operation because the usual provisions for correcting errors in the transmitted indications due to such irregular train movements are not needed.

The fact that the train describer system is independent o'f track circuit operation presents a difiiculty when the system is applied to automatic route control which has already been referred to, and which is overcome, as already explained, by controlling the change-over relay APBS in Asuch a manner that the automatic route control remains effective only asy long as each approaching train registers a route indication and thereby operates relay MSR.

The interlockingcontrol system shown in Figs. 1B to 1F, inclusive, is of the route type and corresponds generally to the system disclosed and claimed in Letters Patent of the United States, No. 2,301,297, granted November 10, 1942, to L. V. Lewis. In this system the routes are set up and their entering signals cleared by the operation of push buttons PB, shown in Fig. 1B, which designate the opposite ends of the routes.

The push button ZPB, shown in Fig. 1B, for the entrance end of the automatically controllable routes, is arranged in accordance with the requirements of my invention to include a rotatable contact d for conditioning the system for manual or automatic control, in addition to the usual push contacts a and b and pull contact c. In the manual control position the button ZPB controls the associated selecting relays by the operation of a repeating relay ZPBR over its contacts a and d, and its functions are similar to those of the others.

The circuits for the selecting relays of Fig. 1B are connected to terminal B of the local source of current at a front contact b of the track relay 1TR or ZTR for the track section at the entering end of the corresponding route, and to terminal N of the same source over wires 25 and 25 and back contacts of the switch control and indication relays of Fig. 1C as hereinafter traced in detail. For a general understanding of the mode of operation it will suffice to point out that when the system is in the condition shown the pressing of button ZPB operates relay ZPBR and thereby energizes the selecting relays ANE and RE for the diverging routes 2 6 and 2 8, button 4PB controls the selecting relay BNE for route 4-8, button 6PB controls the selecting relay ANW for route 6 2, and button SPB controls the selecting relays RW and BNW for the diverging routes 8 2 and 8 4.

Each selecting relay, when operated, is held energized over a stick circuit including its own front contact a, the pull contact of the associated push button, and contact b of the track relay lTR or ZTR for t-he track section at the entrance end of the route.

The operation of the selecting relay for either of two converging routes prevents the operation of the other by the opening of its back 4contact e, as shown for relays RE and BNE, and `also for the similar relays RW and ANW. Each operated selecting relay also opens, at its back contact b, the pickup circuit for the selector relay for the opposing route, as shown for relays ANE and ANW, RE and RW, and BNE and BNW.

In addition, each operated selector relay, by closing its front Contact b or c, conditions an exit stick relay XS for operation by the push button for the exit end of its route. Thus, relay 6X8 is controllable by button 6PB when relay ANE is energized, and relay SXS is controllable by button SPB when either relay RE or BNE is energized. Likewise, relay 2X8 is controllable by relay ZPBR when either relay ANW or RW is energized and relay 4XS is controllable by button 4PB when relay BNW is energized.

Under automatic operation, relay APBS is energized and its contacts b and c complete circuits by which a repeating relay AP or BP for the indication storage relay A1 or B1 of the train describer system is energized concurrently with the display of a route indication for route 2 6 or 2 8 by lighting lamp AE or BE. By closing its contacts a and b relay AP energizes relays ANE and 6X3, or relay BP energizes relays RE and 8XS, with the same effect as when these relays are energized by manual control.

The energization of an exit relay XS closes a circuit in Fig. 1C for a relay NLP or RLP, depending upon whether the switches are to be operated to normal or reverse for the selected route. These relays are identified as lever repeater relays because they may also be operated by moving a normally inactive emergency switch lever 1SW to its respective normal and reverse positions.

When relay NLP is energized, its back contact e interrupts the circuits for relays RE and RW, and when relay RLP is energized, its back contact e interrupts the circuits for relays ANE, ANW, BNE and BNW. In this manner if two selecting relays ANE and RE or BNW and RW for diverging routes have been energized, the operation of relay NLP by the selected exit relay'releases relay RE or RW, while if relay RLP is operated, it releases relay ANE or BNW.

Relays NWS and RWS are switch operating relays which govern the power operation of the track switches 1A and 1B to their respective normal and reverse positions in the conventional manner. These relays are controlled by relays NLP and RLP over front contacts b and c of a switch locking relay LS which is energized only when it is proper to operate the track switches, its circuits including front contacts d of the track relays lTR and 2TR of Fig. 1A and of an approach locking relay AS, shown in Fig. 1F, for each signal which governs traflic movements over switch 1A or 1B.

The operation of relay NLP or RLP to be effective must be made at a time when relay LS is already energized, otherwise relay LS is prevented from picking up by the opening of back contact b of relay NLP or RLP.

When the track switches 1A and 1B complete their operation in response to the operation of relay NWS or RWS a switch correspondence relay NWC or RWC becomes energized and picks up the associated indication relay NWK or RWK, and the latter completes a circuit in Fig. 1D, prepared by the operated exit relay XS, for a route check relay RR which selects the entering signal for the route.

The operated route relay RR, by opening its back contact c in Fig. 1F releases the approach locking relay AS for the entering signal and this relay in turn releases relay LS in Fig. 1C. Relays LS by closing its back contact d or e maintains the operated indication relay NWK or RWK energized. If relay NWK is energized, its contact c maintains the circuits for relays RE and RW open, while if relay RWK is energized, its contact c maintains the circuits for relays ANE, ANW, BNE and BNW open. This prevents the selection of any route which conilicts with the one established, as long as the switch locking is effective. The opening of contact c of the approach locking relay AS for the entering signal in Fig. 1B prevents the reversal of the traffic direction over an established route.

In addition, relay LS closes a back contact f or g in Fig. 1E to complete a circuit for the mechanism for the entering signal for the selected route (identified by the reference character G prefixed by the designation of the signal) and the operated mechanism G opens its contact a in the circuit for the associated locking relay AS to hold that relay released until the signal is restored to stop.

A route established in this manner may be cancelled manually by momentarily pulling the button PB for the entrance end, to open its contact c. This releases successively the operated selecting and exit relays, relay NLP or RLP, the operated relay RR and the operated signal mechanism G.

The closing of back contact a of this mechanism G and of back contact c of the associated route relay RR completes a circuit for a time element relay ITER or ZTER, over a back contact a of the associated approach locking relay AS and a front Contact g of the track relay lTR or ZTR. The time element relay first opens a quick acting checking contact c in the signal mechanism circuit and then after a predetermined time locking period closes its timing contact a or b in the circuit for the controlling relay AS causing that relay to pick up to energize relay LS, and to open the circuit for the time eleent relay, which then returns to its initial condition in which its checking contact c is closed. Relay LS releases relay NWK or RWK to enable a conicting route to be established.

When the system is conditioned for manual control,

the approach locking relay is reenergizediautomatically as soon as a train accepts the signal :and enterstherst section of the route. ln this casev the 'operated selecting relay is released by the opening of contact b of the track relay lTR or ZTR, and lthe selecting relaythen releases the operated exit relay `XS which in turn releases relay NLP or RLP and the operated route relay RR. The signal mechanism G is released concurrently by the opening of contact c of the track relay 1'I`R or ZTR, andV the associated approach locking relay AS is picked up at once over a back contact e or f ofthe trackrelay. The opening of front contact g of the track relay prevents unnecessarily setting the time element relayinto operation which otherwise would occur with each train passage.

Although the approach locking relay AS is picked up automatically as the result of the passage of a train while the switch section is occupied, the switch locking relay LS is held released by the open front contact d of the track relay lTR or ZTR, and relay LS holds relay INWK or IRWK energized, so that the switch locking remains etective until the train vacates the switch section.

In Fig. 1F each of the pickup circuits for an approach locking relay AS which includes a back contact e or f of a track relay includes in series therewith a front contact a, b, c or d of a quick release, slow pickup relay POSR which is normally energized by current from terminals BX and NX of the alternating current track circuit power supply. f

The purpose of relay POSR is to insure against the premature energization of anA approach locking relay AS during the time locking period imposed by `relay ITER or ZTER in the event the track relay is released as a result of the temporary interruption of the alternating current power supply. This arrangement is disclosed and claimed in Letters Patent of the United States No. 2,167,027, granted July 25, 1939, to C. H. Lay.

lf the system is conditioned for automatic control, the approach locking relay for the entering signal is not reenergized automatically when a trainj enters the automatically controllable route 2 6 or 2 8, for the reason that the circuit for the approach locking relay vZAS for that signal which includes Contact e of the track relay lTR is held open at back contact e of the change-over relay APBS, and in this case, relay ZAS is reenergized by the operation of the time element relay ITER, at the end of a predetermined time locking period which begins when the train vacates the route and the track relay ITR becomes energized, in the case of route 2 6, or when relays 1TR and ZTR are both energized in the case of route 2 8.

Relays 4AS and SAS are controlled ina similar manner over back contacts f and g of relay APBS, for the reason that these relays are associated with routes 4 8 and 8 4 which conflict with the automatically establishable routes and which may be set up by manual controlV when the system is conditioned for automatic operation.

As already mentioned, front contact g of the track relay is included in the circuit for the time element relay `to prevent its unnecessary operation when the approach locking relay is picked up automatically over aiback contact of the track relay. Under automatic operation these contacts serve a diierent purpose,which is to insure that the time element relay does not -begin operation until the route is fully vacated, and for that reason an Vadditional contact h of the track relay ZTR is require-d in the circuit for the time element relay ITER.

The operation of the apparatus of my invention under diterent assumed conditions will now be described, assuming first that the operator sets 'up the system for automatic route control Aof an approaching train equipped with a marker coil tuned to frequency f1.

The operator rotates button ZPB to the right to close its contact d and then presses it to momentarily close its contacts a and b. i y

The change-over relay APBS picks up over the circuit, from terminal N at contact d of button ZPB in its right- Ihand position, which includes the winding of relay APBS, contact b of button IZPB, wireZl, .front contacts a of relays ZTR, 1TR and ZAR and extends to terminal B at front contact b of the track relay 14TR. When button ZPB is released, relay APBS is held energized over the stick circuit which extends to terminalvN over the right-hand contact d of button ZPB, and to terminal B over its own front contact a, wire 22 and contact b of relay MTR.

When the train passes the reporting device TD1, the train carried coil effectively couples the primary coil supplied with current of frequency f1 to its secondary coil causing the detector relay AD to be momentarily energized. v

The closing of contact a of relay AD energizes the directional stick relay MSR over front contact c ofthe track relay 14TR. Relay 14SR is arranged to have an adequate release period, normally several seconds, by the provision of a condenser of large capacity in parallel with its winding. The reporting device TD1 is so placed with reference to the location of the vehicle carried marker coil at the time the track relay is shunted due to the passage of the first pair of Wheels of the vehicle over the insulated joints between sections 16T and 14T, that the track relay 14TR will release while relay 14SR is still in its energized position and will complete a stick circuit for relay 14SR which includes its winding and front contact a, and back `contact c of relay 14TR.

By closing its front contact b, relay 14SR maintains relay APBS energized during the time the train is traversing section 14T. It has already been explained that the block section provides an overlap to prevent two trains from occupying the same section, and it follows that relay 14TR will pick up `to release relay MSR before a following train can enter section 14T.

In the storage unit system, relay L2 is held energized over the stick circuit which includes its own front contact a and the back contacts Va of the storage relays of the second storage unit, and when relay AD is operated, relay AZ is picked up over contacts b of relays LZ and AD. Relay A2 is held energized overl a stick circuit including its own front contact a. It will be noted that the pickup and stick circuits for relay AZ have two connections to terminal B, one over back contact d of relay L1 and the other over,back contacts d, in series, of relays A1, B1 and N1.

When relay AZ picks up it releases relay LZ, and energizes relay L1 over the circuit from terminal N which includes the back contacts c of relays A1, B1 and N1, the winding of relay L1, front contact d of relay A2, back contacts d of relays BZ and N2, and terminal B.

When relay L1 picks up it establishes a stick circuit over its contact a and completes a pickup circuit for relay A1 which includes front contacts b of relays L1 and A2, and it also opens one branch of the holding circuit for relay A2. Relay A1 picks up and completes a stick circuit at its contact a so that it remains energized. Relay A1 also opens the other branch of the stick circuit for relay AZ so that relay AZ releases, with the result that relay L1 releases and relay LZ is reenergized.

When relay A1 is energized, lamp AE is lighted over its contact e to display the indication for route 2 6, and relay AP in Fig. 1B is energized over front contact b of relay APBS, wire Z3, and contact b of relay A1.

When relay AP picks up, it energizes relay ANE over the circuit which extends to terminal B over front contact b of relay 1TR, front contact tz of relay AP, back contact b of relay ANW, and to terminal N over back Contact e of relay RW, wire Z6, back contact e of relay RLP and back contact c of relay RWK.

Relay ANEl picks up and energizes relay 6X8 over the circuit which includes front contact b of relay AP and front contacts c of relays ANE and 6AS.

In Fig. 1C, relay NLP is energized over front contact d of relay 6X8` and back contact a of relay RLP. Since thetrack switches 1A and 1B are already in the position 11 required for route 2 6, with relays NWS and NWC energized,'relay NWK is energized at once over contact d of relay NLP and contact a of relay NWC.

In Fig. 1D, relay ZRR is energized by the closing of front contact b of relay NWK and front contact c of relay 6XS.

In Fig. 1F, the opening of back contact c of relay ZRR releases the approach locking relay ZAS, which by opening its contact d in Fig. 1C, releases relay LS.

In Fig. 1E, mechanism 2AG is now energized over the route circuit from terminal B over front contacts b of relays 6AS and NWC, back contact f of the switch locking relay LS, the quick acting check contact c of the time element relay 1TER, front contact c of the track relay 1TR, back contact b of relay ZAS, front Contact a of relay ZRR, front contact c of relay NWC, the winding of the mechanism 2AG for signal 2A, back contact c of relay RWC and front contact b of relay 2RR to terminal N.

It is to be understood that the indication displayed by the signal changes from stop to proceed or caution, when its mechanism is energized, to authorize the train to enter the established route.

Before tracing the further movement of the train for which the route has been established, it will be assumed that a second train, equipped with a marker coil tuned to frequency f2, passes the reporting device TD1 before the rst train passes the reporting device TD2.

When the second train passes the reporting device TD1, relay BD will be momentarily energized and will energize relays B2 and 14RS, and relay B2 will release rclay L2, by operations similar to those already described, and relay 14SR will be effective to maintain relay APBS energized during the passage of the train through section 14T as in the preceding example.

Since relay A1 is energized, relay L1 is held released and the route indication for the second train is stored by relay B2 of the second unit.

The second reporting device TD2 may be located a short distance in the rear of signal 2A, and it will be assumed that the rst train has advanced to a point where its marker coil has passed the device TD2 but that the train has not yet passed signal 2A to shunt the track relay 1TR.

When the marker coil on the rst train passes the device TD2, relay CN is momentarily energized and releases relay A1, cancelling the indication displayed by lamp AE and releasing relay AP. By closing its back contacts c and d, relay A1 energizes relay L1 and maintains the stick circuit for relay B2 closed after relay L1 picks up, and relay L1 picks up and completes the pickup circuit for relay B1 which includes contacts b of relays B2 and L1 so that relay B1 becomes energized and releases relay B2 which in turn releases relay L1. Relay B1 lights lamp BE to display the indication for route 2 8 for the second train and also energizes relay BP over wire 24 and contact c of relay APBS.

In Fig. 1B, relays ANE and 6XS remain energized over their respective stick circuits and the established or by the energization of relay BP. Relay RE does not operate on closing Contact a of relay BP because the connection to terminal N for relay RE over wire 25 is open at contact e of relay NLP and also at contact c of relay NWK. Relay SXS is not operated by relay BP because its circuit, which includes contact b of relay BP, back contact c of relay BNE and front contacts c of relays RE and SAS, is open at contact c of relay RE.

It will be evident therefore that the change in the route indication is without any effect upon the established route and that signal 2RA will continue to display its indication.

When the first train accepts signal 2A and enters section 1T, the track relay 1TR releases and in turn, re-

route is not interfered with by the release of relay AP ,60

l12 leases relays ANE, 6XS, NLP and ZRR, and deenergizes mechanism 2AG to put signal 2A to stop.

When the rst train vacates route 2 6, relay lTR picks up and completes a -circuit in Fig. 1F for the time element relay 1TER which may be traced from terminal B over back contact c of relay ZRR, back contacts a of mechanisms 2AG and ZBG and of relay ZAS, front contact g of relay 1TR, front contact f of relay NWC through relay 1TER to terminal N.

Relay 1TER becomes energized and opens its quick acting contact c in Fig. 1E, and after a predetermined time interval, closes its contacts a and b in Fig. 1F, the closing of contact a causing relay ZAS to become energized to complete its stick circuit and to release relay 1TER. Since relays NLP and RLP are released, relay ZAS energizes relay LS which in turn releases relay NWK.

When relay NWK releases, terminal N is again connected to the circuits for relays RE and RW, and if relay BP is energized, relays RE, 8XS and RLP will become successively energized and will nd relay LS in its picked-up position; relay RWS will become energized, relays NWS and NWC will release, switches 1A and 1B will assume their reverse position, and relays RWC and RWK will become energized. Relay ZRR will be energized over back contact c of relay ZXS, front contact b of relay RWK and front contact c of relay SXS. This releases relay ZAS, which will release relay LS and complete the route circuit in Fig. 1E which extends from terminal B at front contact b of relay SAS over contacts c of relays ZTR and ZTER, contact b of relay RWC, contact f of relay LS, contacts c of relays 1TER and 1TR, back contact b of relay ZAS, contact a of relay ZRR, back contact c of relay NWC, the winding of mechanism ZBG, front contact c of relay RWC and contact b of relay-ZRR to terminal N, thereby clearing signal 2B for route 2 8.

The locking of the track switches by the time locking means is effective to prevent their operation as long as there is a train in any route which conicts with the one which is establishable automatically by the operation of relay AP or BP by the train describer system even though a track relay is imperfectly shunted during the passage of the train.

The establishment of route 2-8 automatically, as described above, is prevented during the passage of a train over route 2 6 because relay ZAS is held released by the opening of back contact e of relay APBS until contact a of relay 1TER closes at the end of a time locking period which begins when front contact g of relay 1TR closes.

Similarly, the establishment of route 2 6 automatically during the passage of a train over route 2 8 is prevented until the end of a time locking period which begins when the train vacates the last section 2T of the route and closes contact h of relay 2TR, which in this case is included in series with contact g of relay 1TR because contact f of relay NWC and contact d of relay APBS are both open.

When the system is conditioned for automatic operation, route 4 8 or 8 4 may be set up manually by operation of the push buttons 4PB and SPB, provided route 2 8 has not been already established to open contact c of relay RWK in the circuit for the selecting relays BNE andBNW. The establishment of route 2 8, but not of route 2 6, is prevented during thepassage of a train over route 4 8 or 8 4 because relay LS is held deenergized by the release of relay 4AS or SAS, and thc latter relay is held released by the opening of back contact j" or g-of relayvAPBS until contact a or b of relay 2TER closes at the end of a time locking period which begins when front contact g of relay ZTR closes.

A back contact of relay APBS is not included in the circuit for relay 6AS because this relay is released only when route'6, 2 is setup, and neither this route nor route `13 8-2 can be `set up when the vsystem is conditioned for automatic operation.

An important condition is to be considered is when two successive trains have `the same route. In this case relay AP or BP is released when the first train passes thel second reporting device TD2 and fthesame relay is then reenergized by the route indication 'for Vthe second train. The route selecting relay ANE or is released by the track relay lTR and is reenergized by-this relay when the first train vacates section 1T, so that signal 2A or 2B for the same route will clear for the second train -as soon as the first train passes out ofthe block, which may be assumed to include one or more sections in advance of the switch sections, the circuits for which are not shown. No time delay is imposed fas when the route for the second train is different from that of Athe first train, the switch locking remaining in effect in Athis case.

It will next be assumed that the system is conditioned for automatic operation, with relay APBS energized, that route 2 6 or 2 8 has Vbeen set-up and vsignal 2A or 2B cleared for an approaching train by the .operation of relay AP or BP, and that -a following train which is equipped with a marker coil tuned to frequency f3 enters the approach zone. On passing the reporting device TD1, relay ND will be operated to energize relay N2 which will store the indication until conditions permit its transfer to relay N1. The directional stick `relay '14SR will not be operated and in consequence the change-over relay APBS will be released bythe track relay MTR, thereby releasing relay AP or BP. When the first train enters the route, relay ZAS is picked up bythe release of the track relay lTR and the switch locking is released as soon as the train vacates the route.

In the event the `second train is not equipped with a marker coil and the train reporting device is not actuated, the approach of the train is detected by the release of the track relay 14TR and relay APBS is `released with the same effect as in the preceding example.

In either case, the operator will place contact d in its left-hand position and manually set up the route for the second train.

Although I have herein shown and described only one embodiment of my invention, it is to be understood that various changes and modifications maybe made therein within the scope of the appended claims without depart ing from the spirit and scope `of my invention.

Having thus described my invention, what `I claim is:

l. In an automatic route control system for railroads, a train describer system for supplying indications of the routes for approaching trains in the order lof ztheir approach, a manually controllable yinterlocking control system for establishing routes for said trains corresponding to the route indications supplied by said train describer system, a change-over relay which .is released when said interlocking control sytemis conditioned `'for manual operation and which when energized conditions said interlocking control system to automatically establsh traffic routes in accordance with the indications supplied by said train describer system, manually roperablelmeans for energizing said change-over relay, and track circuit controlled means for maintaining said change-over relay energized only so long las route indications for the appreaching trains continue to betsupplied by said train describer system.

2. In an automatic route control system for railroads, a train describer -systemffor.supplying indications of the routes for approaching trains in the order of` their approach, a manually controllable interlocking control system for establishing routes for said trains corresponding to the route indications supplied byisaidtrain describer system, manual change-over means which in a first position conditions said interlocking control system for man- Vual control and in a second position enables it to be conditioned for automatic control by said train describer system, a change-over relay having pickup land stick circuits rincluding a contact closed by said manual changeoverrneans in its second position, said pickup circuit including a normally open manually operable contact and contacts which when closed indicate that there is no train occupying the routes indicated Aby said train describer system, and `means effective when said change-over relay is energized vfor conditioning said interlocking control system to automatically establish traic routes in accordance with the indications supplied by said train describer system.

3. In an automatic route control system for a stretch of railway track including an interlocking plant and an adjoining approach zone, a train describer system for `registering indications of the routes for trains entering Iwhich is released when said interlocking system is conditionedfor manual operation and which when energized conditions said interlocking control system to automatically establishtraflic routes in accordance with 'the indications registered by said train describer system, manually operable means for energizing said change-over relay, track circuit means for indicating when an approaching train enters said approach zone, and means controlled by said track circuit means for releasing said change-over relay when a train enters said approach zone unless an indication for its route is registered by said train describer system.

4. In an automatic route control system for a stretch of railway track including an interlocking plant and an adjoining approach zone, a train describer system for registering indications of the routes for trains entering Vsaid `approach zone, a manually controllable interlocking control system for establishing routes for such trains `through said interlocking plant, achange-over relay which 4is released when said interlocking system is conditioned for manual operation and which when energized conditions said interlocking control system to automatically establish traic routes in accordance with the indicatact is open due to the presence of a train in said approach zone, said means being effective only if the train .describer system has registered an indication of the route for such train.

5. In an automatic route control system for a stretch of railway track including an interlocking plant and an ladjoining approach zone, a train describer system for registering indications of the routes for trains entering said approach zone, a manually controllable interlocking control system for establishing routes for such trains rthrough said interlocking plant, a change-over relay which is released when said interlocking system is conditioned for manual operation and which when energized conditions said interlocking control system to automatically establish traic routes in accordance with the indications registered by said train describer system, a manually `controllable pickup circuit for said change-over lrelay including contacts responsive to thepresence of a train in lsaid stretch which are closed to enable the relay to be energized only when there is no train in said approach zone or in any portion of a route vcontrollable by said train describer system, a vstick circuit effective to maintain said change-over relay energized during the passage of a train through said stretch, `and manually controllable means for opening said stick circuit.

6. In an automatic route control system for railroads, a train describer system for registeringindications ofthe routes for approaching trains in the order of their approach, an interlocking control system of the type having push buttons for the ends of interlocked traffic routes by means of which such routes may be manually established, means comprising a rotatable contact associated with the push button for the entrance end of the routes indicated by said train describer system, said contact having a first position in which said push button is conditioned for the manual control of such routes and a second position in which the momentary operation of the push button associated therewith conditions the interlocking control system to automatically establish traffic routes in accordance with the indications supplied by said train describer system, and means for terminating the automatic control of said traffic routes upon the approach of a train if a route for such train is not registered by said train describer system.

7. 1n an automatic route control system for railroads, a train describer system controllable by train carried devices and operable independently of trackway conditions to automatically register a distinctive indication when a train passes a first reporting point and to automatically cancel such indication when the same train passes a second reporting point, certain of said indications designating routes to be taken by the corresponding train after passing the second reporting point, an interlocking control system having manually controllable means for establishing said designated routes, a change-over relay which is in a first position when said interlocking control system is conditioned for manual operation and when operated to a second position conditions said interlocking control system to automatically establish the routes designated by said train describer system, manually operable means for operating said change-over relay between said two positions, and means controlled by trackway conditions and effective when said change-over relay is in its second position and a train passes said first reporting point without registering an indication of its route to automatically operate said change-over relay to its first position.

8. In an automatic route control system for railroads, a train describer system having two train reporting de viccs at spaced points controllable by train carried marker devices and adapted to store route indications of successive trains in a series of wayside indicators, means controlled by the marker devices on at least two trains which successively pass the first reporting device for storing their route indications concurrently in said indicator, each train registering its route indication on passing the first reporting device and cancelling such indication on passing the second reporting device, an interlocking control system controllable by said route indications for establishing trafc routes for said trains which correspond to their route indications, a track circuit having a normally energized track relay for indicating the passage of each train irrespective of whether or not it registers a route indication, and means governed by said track relay acting in the event a train passes said first reporting point without registering an indication of its route for preventing the automatic establishment of a route for such train.

9. In combination with a railway track layout which includes interlocked track switches for establishing different trafiic routes, having signals for controlling train movements over the routes, an interlocking control system for establishing said routes, manually operable means for selecting the routes to be established, a train describer system automatically controllable by marker devices on approaching trains for indicating the routes through said layout for such trains, means for automatically selecting certain routes to be established by said interlocking control system in accordance with the route indications supplied by said train describer system, change-over means for establishing said interlocking control system for manual operation in the event a train approaches without affecting said marker devices, switch locking means rendered effective when a route is established and the entering signal conditioned for clearing to prevent the establishment of any coniiicting route, means effective when an established route which conflicts with an automatically establishable route is traversed by a train for maintaining the switch locking for the established route effective for a predetermined time interval after such route is vacated by the train, and means effective when a manually established route which does not conflict with any automatically establishable route is traversed by a train for rendering the switch locking for the established route ineffective as soon as the route is vacated by such train.

10. In combination with a railway track layout which includes interlocked track switches for establishing different traffic routes, having signals for controlling train movements over the routes, an interlocking control system for establishing said routes, manually operable means for selecting the routes to be established, a train describer system automatically controllable by marker devices on approaching trains for indicating the routes through said layout for such trains, change-over means which in a first condition renders said interlocking control system controllable by said manually operable means and which in a second condition renders said interlocking control system controllable to establish certain routes automatically in accordance with the indications supplied by said train describer system, said manually operable means remaining effective to establish routes which do not conflict with any automatically established route, switch locking means for each route which when effective prevents the operation of the switches in such route, means effective when said change-over means is in its first condition for rendering the switch locking for an established route effective from the time its entering signal is conditioned for clearing until it is vacated after the passage of a train over such route, and means effective when said change-over means is in its second condition for maintaining effective the switch locking for an established route from the time its entering signal is conditioned for clearing until the end of a time locking period which begins when the route is vacated after the passage of a train over such route.

11. In an interlocking control system for establishing traffic routes by the operation of interlocked track switches and for controlling signals for governing traffic movements over the routes establishedv by the operation of said switches, manually operable means for operating said track switches and for governing the clearing of said signals, a train describer system adapted to supply route indications to indicate the routes to be taken by approaching trains, means for automatically operating said track switches to establish the routes indicated by said train describer system and for automatically clearing the entering signals for such routes when established, change-over means for establishing said interlocking control system for manual operation in the event a train approaches without affecting said describer system, switch locking means for each route which is effective to prevent the operation of the switches of its route from the time the entering signal therefor s cleared until the route is vacated after the passage of a train over such route, and means for maintaining the switch locking for any route which has been established and which conflicts with an automatically establishable route as long as the established route is occupied by a train and for an additional period of time which begins when the train vacates the established route.

12. In an interlocking control system for establishing traffic routes by the operation of interlocked track switches and for controlling signals for governing traffic movements over the routes established by A the operation of said switches, manually operable means for operating said track switches and for governing the clearing of said signals, a train describer system adapted to supply route indications to indicate the routes to be taken by approaching trains, means for automatically operating said track switches to establish the routes indicated by said train describer system and for automatically clearing the entering signals for such routes when established, change-over means for establishing said interlocking control system for manual operation in the event a train approaches without alecting said describer system, switch locking means for each route which is effective to prevent the operation of the switches of its route from the time the entering signal therefor is cleared until the route is vacated after the passage of a train over such route, means effective when a signal is manually put to stop to prevent the release of the switch locking for the route governed thereby for a predetermined time locking period, and means for maintaining effective the switch locking for any established route which conflicts with an automatically established route as long as the established route is occupied by a train and also for a time locking period which begins when the train vacates said established route.

13. In combination with a railway track layout which includes interlocked track switches for establishing different trafc routes, having signals l.for controlling train movements over the routes, an interlocking control system having manually operable means for operating the track switches to establish said routes and for governing the clearing of the signals for such routes when established, a train describer system which indicates the routes through said track layout to be taken by certain approaching trains, manually operable change-over means effective when operated to enable said train describer system to automatically operate the track switches to establish the routes indicated thereby and to condition the signals therefor for clearing when such routes are established, switch locking means for each route eifective to prevent the establishment of any conflicting route from the time the signal for such route is conditioned for clearing until the route is vacated after the passage of a train or for a time locking period in the event the route is not occupied and the signal for such route is manually put to stop, non-storage means eiective to prevent the establishment of a route by the manually operable means therefor in the event such means is operated at a time when the switch locking for such route is effective, and means associated with the switch locking means for each route which conflicts with one which is automatically establishable by said train describer system `for maintaining such switch locking means effective for a time locking period following the passage of a train over such conicting route.

14. In an interlocking control system, an approach locking relay for preventing the operation of track switches in a trafiic route governed by a railway signal, manual control means and automatic control means for establishing said traliic route and for clearing said signal, a normally closed stick circuit for said relay including its winding and front contact, a second contact which is closed only when the signal indicates stop, and a third contact opened by the signal control means to condition the signal for clearing, a track relay lfor the irst Section 0f such route, a time element relay, a change-over relay which is released when the signal is conditioned for manual control and which when energized conditions the signal for automatic control, two pickup circuits for the approach locking relay which include said second and third contacts, one including back contacts of said change-over relay and track relay in series, the other including a contact closed by the time element relay following its energization for a time locking period, and a circuit for energizing said time element relay including said second and third contacts, a back contact of said approach locking relay, and a front contact of the track relay.

15. In an interlocking control system, an approach locking relay -for preventing the operation of track switches in a traic route governed by a railway signal, manual control means and automatic control means for establishing said traic route and for clearing said signal, a normally closed stick circuit for said relay including its winding and front contact, a second Contact which is .closed only when the signal indicates stop, and a third contact opened by the signal control means to condition the signal for clearing, a track relay for each section of such route, a time element relay, a change-over relay which is released when the signal is conditioned for manual control and which when energized conditions the signal for automatic control, two pickup circuits for the approach locking relay which include said second and third contacts, one including back contacts of the changeover relay and of the track relay for the first section of the route in series, the other including a contact closed by the time element relay lfollowing its energization for a time locking period; and a circuit for energizing said time element relay which includes said second and third contacts and a back contact of said approach locking relay, said circuit including a front contact of the track relay for each section of the route when the change-over relay is energized, and a front contact of the track relay for the rst section only of the route when the changeover relay is released. a

References Cited in the file of this patent UNITED STATES PATENTS 2,030,924 Kemmerer Feb. 18, 1936 2,046,180 Pflasterer June 30, 1936 2,060,485 Bell Nov. 10, 1936 2,122,358 Preston lune 28, 1938 2,171,756 Lewis Sept. 5, 1939 2,184,544 Brooks et al. Dec. 26, 1939 2,194,352 Brixner et al. Mar. 19, 1940 2,255,142 Wight Sept. 9, 1941 2,520,838 Hays Aug. 29, 1950 2,576,038 Pascoe et al Nov. 20, 1951 2,591,036 Young Apr. 1, 1952 2,592,704 Jerome et al Apr. 15, 1952 2,670,434 Groenendale Feb. 23, 1954 

